This invention relates generally to apparatus for sorting fruit, and, more particularly, to apparatus for optically measuring the volume of individual, generally spherical fruit.
The ability to sort fresh fruit according to its volume is essential to the fresh fruit industry. In particular, since spherical fruit, such as oranges and grapefruit, are frequently sold in cartons having a fixed interior volume, it is important that each carton be filled with fruit of a consistent volume. Excessive fruit volume variation can prevent the carton from meeting legal size standards. In addition, sales of the fruit can be affected adversely if the cartons suffer from any of the following three appearance problems. The carton can be a "slack pack", where the average size of the fruit in the carton is too small, a "high pack", where the average size of the fruit is too large, thereby causing fruit compression, splitting, and excessive decay, or a "variable pack", where the average size of the fruit varies excessively.
Initially, the sorting of fruit by volume was performed by manual human labor. In addition to being a slow and costly process, manual sorting has proven to be inaccurate in that the workers' assessments are highly subjective, varying both with time and from worker to worker. As a result, substantial effort has been expended to automate the sorting process.
Mechanical sizers have been used for many years to measure the volume of generally spherical fruit. Such sizers typically include a series of spaced, parallel rollers, each containing a number of four-point contact rubber grommets. Unfortunately, the sizers are completely accurate only when the fruit are perfectly spherical. If the fruit have an irregular shape, they frequently are not oriented effectively in the four point grommet and an inaccurate volume measurement results.
Another drawback to mechanical sizers is their relative high cost. Since the demand for sizing apparatus is very limited, and since mechanical sizers typically require many specialized parts not otherwise manufactured in voluem, they tend to be very costly. Maintenance costs are also high.
Optical sizing apparatus can be substantially less expensive and more accurate than mechanical sizers. Such optical apparatus have been used in the past to measure the height and width of a succession of parallel slices or cross-sections of an article as it is moved through an examining region. These heights and width measurements are then used to produce a measure of the article's total volume. However, such apparatus are not entirely suitable for use in measuring the volume of fruit. This is especially the case when reflective debris is also present in the examining region, or when non-reflecting blemishes are present on the skin of the fruit.
It will be appreciated from the foregoing that there is a need for an optical apparatus for more accurately measuring the volume of individual spherical fruit even in the presence of light-reflecting objects adjacent to the fruit or blemishes on the skin of the fruit. The present invention fulfills this need.